Projection system and projector

ABSTRACT

A projection system includes a first optical system and a second optical system including an optical element and a reflector and disposed at the enlargement side of the first optical system. The optical element has a reflection surface, a first transmissive surface disposed at the enlargement side of the reflection surface, and a second transmissive surface disposed at the enlargement side of the first transmissive surface. The reflector is disposed at the enlargement side of the reflection surface and at the reduction side of the first transmissive surface. The reflector is disposed between the optical element and the first optical system in the direction along a first optical axis of the first optical system.

The present application is based on, and claims priority from JP Application Serial Number 2020-008952, filed Jan. 23, 2020, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a projection system and a projector.

2. Related Art

JP-A-2010-20344 describes a projector that enlarges and projects a projection image formed by an image formation section via a projection system. The projection system described in JP-A-2010-20344 is formed of a first optical system and a second optical system sequentially arranged from the reduction side toward the enlargement side. The first optical system includes a refractive optical system. The second optical system is formed of a reflection mirror having a concave reflection surface. The image formation section includes a light source and a light valve. The image formation section forms a projection image in the reduction-side image formation plane of the projection system. The projection system forms an intermediate image in a position between the first optical system and the reflection surface and projects a final image on a screen disposed in the enlargement-side image formation plane of the projection system.

The projection system and the projector are required to have a shorter projection distance. An attempt to further shorten the projection distance in the configuration using the projection system described in JP-A-2010-20344, however, causes a problem of a difficulty in designing the projection system.

SUMMARY

To solve the problem described above, a projection system according to an aspect of the present disclosure include a first optical system and a second optical system including an optical element and a reflector and disposed at an enlargement side of the first optical system. The optical element has a reflection surface, a first transmissive surface disposed at the enlargement side of the reflection surface, and a second transmissive surface disposed at the enlargement side of the first transmissive surface. The reflector is disposed at the enlargement side of the reflection surface and at a reduction side of the first transmissive surface. The reflector is disposed between the optical element and the first optical system in a direction along a first optical axis of the first optical system.

A projector according to another aspect of the present disclosure includes the projection system described above and an image formation section that forms a projection image in a reduction-side image formation plane of the projection system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a projector including a projection system.

FIG. 2 is a light ray diagram diagrammatically showing the entire projection system according to Example 1.

FIG. 3 is a light ray diagram of the projection system according to Example 1.

FIG. 4 is a light ray diagram of a second optical system of the projection system according to Example 1.

FIG. 5 shows the enlargement-side MTF of the projection system according to Example 1.

FIG. 6 is a light ray diagram diagrammatically showing the entire projection system according to Example 2.

FIG. 7 is a light ray diagram of the projection system according to Example 2.

FIG. 8 is a light ray diagram of the second optical system of the projection system according to Example 2.

FIG. 9 shows the enlargement-side MTF of the projection system according to Example 2.

FIG. 10 is a light ray diagram diagrammatically showing the entire projection system according to Example 3.

FIG. 11 is a light ray diagram of the projection system according to Example 3.

FIG. 12 is a light ray diagram of the second optical system of the projection system according to Example 3.

FIG. 13 shows the enlargement-side MTF of the projection system according to Example 3.

FIG. 14 is a light ray diagram diagrammatically showing the entire projection system according to Example 4.

FIG. 15 is a light ray diagram of the projection system according to Example 4.

FIG. 16 is a light ray diagram of the second optical system of the projection system according to Example 4.

FIG. 17 shows the enlargement-side MTF of the projection system according to Example 4.

FIG. 18 is a light ray diagram diagrammatically showing the entire projection system according to Example 5.

FIG. 19 is a light ray diagram of the projection system according to Example 5.

FIG. 20 is a light ray diagram of the second optical system of the projection system according to Example 5.

FIG. 21 shows the enlargement-side MTF of the projection system according to Example 5.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A projection system according to an embodiment of the present disclosure and a projector including the projection system will be described below in detail with reference to the drawings.

Projector

FIG. 1 is a schematic configuration diagram of a projector including a projection system 3 according to the present disclosure. A projector 1 includes an image formation section 2, which generates a projection image to be projected on a screen S, the projection system 3, which enlarges the projection image and projects the enlarged image on the screen S, and a controller 4, which controls the action of the image formation section 2, as shown in FIG. 1.

Image Generation Optical System and Controller

The image formation section 2 includes alight source 10, a first optical integration lens 11, a second optical integration lens 12, a polarization converter 13, and a superimposing lens 14. The light source 10 is formed, for example, of an ultrahigh-pressure mercury lamp ora solid-state light source. The first optical integration lens 11 and the second optical integration lens 12 each include a plurality of lens elements arranged in an array. The first optical integration lens 11 divides the light flux from the light source 10 into a plurality of light fluxes. The lens elements of the first optical integration lens 11 focus the light flux from the light source 10 in the vicinity of the lens elements of the second optical integration lens 12.

The polarization converter 13 converts the light via the second optical integration lens 12 into predetermined linearly polarized light. The superimposing lens 14 superimposes images of the lens elements of the first optical integration lens 11 on one another in a display region of each of liquid crystal panels 18R, 18G, and 18B, which will be described later, via the second optical integration lens 12.

The image formation section 2 further includes a first dichroic mirror 15, a reflection mirror 16, a field lens 17R, and the liquid crystal panel 18R. The first dichroic mirror 15 reflects R light, which is part of the light rays incident via the superimposing lens 14, and transmits G light and B light, which are part of the light rays incident via the superimposing lens 14. The R light reflected off the first dichroic mirror 15 travels via the reflection mirror 16 and the field lens 17R and is incident on the liquid crystal panel 18R. The liquid crystal panel 18R is a light modulator. The liquid crystal panel 18R modulates the R light in accordance with an image signal to form a red projection image.

The image formation section 2 further includes a second dichroic mirror 21, a field lens 17G, and the liquid crystal panel 18G. The second dichroic mirror 21 reflects the G light, which is part of the light rays via the first dichroic mirror 15, and transmits the B light, which is part of the light rays via the first dichroic mirror 15. The G light reflected off the second dichroic mirror 21 passes through the field lens 17G and is incident on the liquid crystal panel 18G. The liquid crystal panel 18G is a light modulator. The liquid crystal panel 18G modulates the G light in accordance with an image signal to form a green projection image.

The image formation section 2 further includes a relay lens 22, a reflection mirror 23, a relay lens 24, a reflection mirror 25, a field lens 17B, and the liquid crystal panel 18B. The B light having passed through the second dichroic mirror 21 travels via the relay lens 22, the reflection mirror 23, the relay lens 24, the reflection mirror 25, and the field lens 17B and is incident on the liquid crystal panel 18B. The liquid crystal panel 18B is a light modulator. The liquid crystal panel 18B modulates the B light in accordance with an image signal to form a blue projection image.

The liquid crystal panels 18R, 18G, and 18B surround a cross dichroic prism 19 in such a way that the liquid crystal panels 18R, 18G, and 18B face three sides of the cross dichroic prism 19. The cross dichroic prism 19, which is a prism for light combination, produces a projection image that is the combination of the light modulated by the liquid crystal panel 18R, the light modulated by the liquid crystal panel 18G, and the light modulated by the liquid crystal panel 18B.

The cross dichroic prism 19 forms part of the projection system 3. The projection system 3 enlarges and projects the projection images (images formed by liquid crystal panels 18R, 18G, and 18B) combined by the cross dichroic prism 19 on the screen S. The screen S is the enlargement-side image formation plane of the projection system 3.

The controller 4 includes an image processor 6, to which an external image signal, such as a video signal, is inputted, and a display driver 7, which drives the liquid crystal panels 18R, 18G, and 18B based on image signals outputted from the image processor 6.

The image processor 6 converts the image signal inputted from an external apparatus into image signals each containing grayscales and other factors of the corresponding color. The display driver 7 operates the liquid crystal panels 18R, 18G, and 18B based on the color projection image signals outputted from the image processor 6. The image processor 6 thus causes the liquid crystal panels 18R, 18G, and 18B to display projection images corresponding to the image signals.

Projection System

The projection system 3 will next be described. Examples 1 to 5 will be described below as examples of the configuration of the projection system 3 incorporated in the projector 1. In the light ray diagrams of the projection system according to Examples 1 to 5, the liquid crystal panels 18R, 18G, and 18B are referred to as liquid crystal panels 18.

Example 1

FIG. 2 is a light ray diagram diagrammatically showing the entire projection system according to Example 1. FIG. 2 diagrammatically shows light fluxes F1 to F4, which exit out of a projection system 3A according to the present example and reach the screen S. The light flux F1 is a light flux that reaches a smallest image height position. The light flux F4 is a light flux that reaches a largest image height position. The light fluxes F2 and F3 are light fluxes that reach positions between the position that the light flux F1 reaches and the position that the light flux F4 reaches. FIG. 3 is a light ray diagram of the projection system 3A according to Example 1. FIG. 4 is a light ray diagram of a second optical system in Example 1.

The projection system 3A according to the present example includes a first optical system 31 and a second optical system 32 sequentially arranged from the reduction side toward the enlargement side, as shown in FIG. 3. The first optical system 31 is a refractive optical system including a plurality of lenses. The second optical system 32 includes an optical element 33 and a reflector 34. The optical element 33 has a reflection surface 41, a first transmissive surface 42, and a second transmissive surface 43. The reflector 34 is a flat mirror. In the second optical system 32, the reflection surface 41, the reflector 34, the first transmissive surface 42, and the second transmissive surface 43 are located in the presented order along the light traveling direction from the reduction side toward the enlargement side.

The liquid crystal panels 18 of the image formation section 2 are disposed in the reduction-side image formation plane of the projection system 3A. The liquid crystal panels 18 form the projection images at one side of a first optical axis N of the first optical system 31 in a plane perpendicular to the first optical axis N. The screen S is disposed in the enlargement-side image formation plane of the projection system. An intermediate image 35 conjugate with the reduction-side image formation plane is formed between the first optical system 31 and the reflection surface 41 of the optical element 33. The intermediate image 35 is conjugate also with the enlargement-side image formation plane. The intermediate image 35 is formed at the side opposite the screen S with respect to the first optical axis N of the first optical system 31.

In the following description, three axes perpendicular to one another are called axes X, Y, and Z for convenience. The width direction of the screen S, which is the enlargement-side image formation plane, is called an axis-X direction, the upward/downward direction of the screen S is called an axis-Y direction, and the direction perpendicular to the screen S is called an axis-Z direction. The plane containing the first optical axis N of the first optical system 31 and a second optical axis M of the reflection surfaces 41 of the optical element 33 is called a plane YZ.

The first optical axis N of the first optical system 31 extends in the axis-Z direction in the present example. FIGS. 2, 3, and 4 are each a light ray diagram in the plane YZ. The liquid crystal panels 18 form the projection images at an upper side Y1 of the first optical axis N of the first optical system 31. The intermediate image 35 is formed at a lower side Y2 of the first optical axis N of the first optical system 31. The screen S is disposed at the upper side Y1 of the first optical axis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15 lenses L1 to L15, as shown in FIG. 3. The lenses L1 to L15 are arranged in the presented order from the reduction side toward the enlargement side. In the present example, the lenses L2 and L3 are bonded to each other into a first doublet L21. The lenses L4 and L5 are bonded to each other into a second doublet L22. The lenses L11 and L12 are bonded to each other into a third doublet L23. The lenses L13 and L14 are bonded to each other into a fourth doublet L24. An aperture O is disposed between the lens L7 and the lens L8.

The optical element 33 includes a meniscus lens 36, which has a convex shape at the enlargement side, and a reflection coating layer 37, which is provided on part of the reduction-side surface of the meniscus lens 36. The reflection surface 41 of the optical element 33 is the reflection coating layer 37. The optical element 33 is designed by using the second optical axis M of the reflection surface 41 as the axis in the design stage. In other words, the second optical axis M is the design-stage optical axis of the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The second optical axis M of the reflection surface 41 coincides with the first optical axis N of the first optical system 31, as shown in FIG. 4. The second optical axis M of the reflection surface 41 therefore extends along the axis Z. The reflection surface 41 is located at the lower side Y2 of the second optical axis M. The first transmissive surface 42 and the second transmissive surface 43 are located at the upper side Y1 of the second optical axis M. The reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43 of the optical element 33 are each an aspheric surface. The aspheric surfaces are each a free-form surface in some cases. Also in this case, the free-form surfaces are designed by using the second optical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of the reflection surface 41. The reflector 34 is located at the upper side Y1 of the second optical axis M of the reflection surface 41. The reflector 34 is shifted from the optical element 33 toward the first optical system 31 in the direction along the second optical axis M of the reflection surface 41.

A pupil P of the second optical system 32 is located inside the second optical system 32. The pupil P of the second optical system 32 in the plane YZ is defined by the line that connects an upper intersection 53, where an upper peripheral light ray 51 a of an upper end light flux 51 passing through the axis-Y-direction upper end of an effective light ray range 50 of the second transmissive surface 43 and an upper peripheral light ray 52 a of a lower end light flux 52 passing through the axis-Y-direction lower end of the effective light ray range 50 intersect each other in the plane YZ, to a lower intersection 54, where a lower peripheral light ray 51 b of the upper end light flux 51 and a lower peripheral light ray 52 b of the lower end light flux 52 intersect each other in the plane YZ. The pupil P is formed between the reflector 34 and the second transmissive surface 43. The pupil P inclines with respect to an imaginary vertical line V perpendicular to the second optical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3A are listed below. The surfaces of the lenses are numbered sequentially from the reduction side toward the enlargement side. Reference characters are given to the lenses, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface. Data labeled with a surface number that does not correspond to any of the lenses, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface is dummy data. Reference character R denotes the radius of curvature. Reference character D denotes the axial inter-surface distance. Reference character C denotes the aperture radius. Reference characters R, D, and C are each expressed in millimeters.

Reference Surface Refraction/ character number Shape R D Glass material reflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1 Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity 25.9100 SBSL7_OHARA Refraction 13.3059 3 Spherical Infinity 0.0000 Refraction 16.1679 L1 4 Spherical 27.2275 9.6207 SFPL51_OHARA Refraction 17.2029 5 Spherical −96.6617 0.2000 Refraction 16.8825 L2 6 Spherical 29.0138 7.7348 SFSL5_OHARA Refraction 14.8572 L3 7 Spherical −60.7868 1.2000 STIH6_OHARA Refraction 14.0000 8 Spherical 46.8651 0.2000 Refraction 12.8622 L4 9 Spherical 20.0287 9.3478 SBSL7_OHARA Refraction 12.3016 L5 10 Spherical −22.8718 1.2000 TAFD25_HOYA Refraction 11.5596 11 Spherical 190.2895 0.4397 Refraction 10.9652 L6 12 Aspheric 41.8537 1.2000 LBAL35_OHARA Refraction 10.8731 13 Aspheric 21.5006 0.2000 Refraction 10.4882 L7 14 Spherical 19.3529 7.5650 SFSL5_OHARA Refraction 10.5273 15 Spherical 62.6402 2.2349 Refraction 9.5673 O 16 Spherical Infinity 0.4040 Refraction 9.2670 L8 17 Spherical 29.3227 4.6147 STIH53_OHARA Refraction 10.2078 18 Spherical −68.0342 3.3630 Refraction 10.2526 L9 19 Aspheric −87.2281 5.6840 LLAM60_OHARA Refraction 10.0018 20 Aspheric 20.5876 4.2883 Refraction 11.2693 21 Spherical Infinity 0.2988 Refraction 12.5570  L10 22 Spherical 40.1891 3.9043 STIM22_OHARA Refraction 15.2007 23 Spherical 112.0759 20.7200 Refraction 15.5454  L11 24 Spherical 62.0827 22.5281 STIM2_OHARA Refraction 26.0000  L12 25 Spherical −30.5918 1.2000 STIH6_OHARA Refraction 26.1404 26 Spherical 138.3228 0.2000 Refraction 30.0612  L13 27 Spherical 105.8154 15.0227 STIL25_OHARA Refraction 31.1823  L14 28 Spherical −64.8091 1.3233 STIH6_OHARA Refraction 31.6527 29 Spherical −64.5253 0.2000 Refraction 31.9494  L15 30 Aspheric −338.6023 2.2476 ‘Z-E48R’ Refraction 32.5943 31 Aspheric 45.8885 13.3862 Refraction 32.0721 32 Spherical Infinity 16.7098 Refraction 31.7316 33 Spherical Infinity 39.3523 Refraction 30.1083 41 34 Aspheric −46.4264 −39.3523 Reflection 37.4512 34 35 Spherical Infinity 39.3523 Reflection 38.7046 42 36 Aspheric −50.2503 1.2000 ‘Z-E48R’ Refraction 39.8994 43 37 Aspheric −162.2411 0.0000 Refraction 58.4637 38 Spherical Infinity 439.5080 Refraction 158.9958 S 39 Spherical Infinity 0.0000 Refraction 1487.1211

The aspheric coefficients of each of the aspheric surfaces are listed below.

Surface number S12 S13 S19 Radius of 41.85372823 21.50057506 −87.22813862 curvature in axis-Y direction Conic constant 1.568 −1.3 −1 (k) Fourth-order −1.92815E−04 −1.48851E−04 −7.47776E−05 coefficient (A) Sixth-order 1.53921E−06 1.63590E−06 −7.57612E−09 coefficient (B) Eighth-order −6.56218E−09 −7.90242E−09 −1.24201E−10 coefficient (C) Tenth-order 1.33383E−11 1.76919E−11 coefficient (D) Twelfth-order coefficient (E) Fourteenth-order coefficient (F) Surface number S20 S30 S31 Radius of 20.58762759 −338.6022945 45.88845982 curvature in axis-Y direction Conic constant −0.88 90 0 (k) Fourth-order −3.30064E−05 2.13930E−05 −1.77739E−06 coefficient (A) Sixth-order 6.74245E−08 −1.77680E−08 1.39563E−08 coefficient (B) Eighth-order −1.14226E−10 1.22895E−11 −2.21256E−11 coefficient (C) Tenth-order −1.11769E−14 5.46695E−15 coefficient (D) Twelfth-order 7.16104E−18 4.41203E−18 coefficient (E) Fourteenth-order −2.09326E−21 −2.25037E−21 coefficient (F) Surface number S34 S36 S37 Radius of −46.42641713 −50.2503134 −162.2411346 curvature in axis-Y direction Conic constant −1 0.55805156 6.222885555 (k) Fourth-order 7.13212E−07 −1.95028E−06 −2.69488E−06 coefficient (A) Sixth-order −5.94905E−10 −1.37400E−09 6.44559E−10 coefficient (B) Eighth-order 1.93757E−13 −4.89909E−14 −7.82591E−14 coefficient (C) Tenth-order 7.20821E−18 coefficient (D) Twelfth-order −4.35422E−20 coefficient (E) Fourteenth-order 1.23785E−23 coefficient (F)

A maximum object height, the numerical aperture, a mirror radius, a lens overall length, and TR of the projection system 3A are as follows: The maximum object height is the dimension from the first optical axis N of the projection system 3A to the farthest point therefrom in an image formation region of the surface of each of the liquid crystal panels 18. The maximum object height is expressed in millimeters. The numerical aperture is abbreviated to NA. The mirror radius is the radius of the first reflection surface in millimeters. The final lens radius is the lens radius of the second transmissive surface in millimeters. The lens overall length of the projection system 3A is the distance in millimeters from the liquid crystal panels 18 to the second transmissive surface in the axis-Z direction. TR stands for a throw ratio and is the quotient of the operation of dividing the projection distance by the axis-X-direction dimension of a projection image projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 37.5 Final lens radius 58.5 Lens overall length 232 TR (0.59″WXGA) 0.27

Effects and Advantages

The projection system 3A according to the present example includes the first optical system 31 and the second optical system 32 sequentially arranged from the reduction side toward the enlargement side. The second optical system 32 in the projection system 3A includes the optical element 33, which has the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43, and the reflector 34. The reflection surface 41, the reflector 34, the first transmissive surface 42, and the second transmissive surface 43 are located in the presented order along the light traveling direction from the reduction side toward the enlargement side. The reflector 34 is located between the optical element 33 and the first optical system 31 in the direction along the first optical axis N of the first optical system 31.

In the projection system 3A according to the present example, the first transmissive surface 42 and the second transmissive surface 37 can refract the light flux reflected off the reflection surface 41 and the reflector 34 in the second optical system 32. The projection distance of the projection system is therefore readily shortened as compared with a case where the second optical system has only the reflection surface. In other words, the projection system 3A according to the present example can have a short focal length as compared with the case where the second optical system has only the reflection surface.

The projection system 3A according to the present example, which includes the reflector 34, can output the light flux having exited out of the second optical system 32 toward the side opposite the first optical system 31 in the axis-Y direction. The light flux that exits out of the second optical system 32 is therefore readily oriented in a direction in which the light flux does not interfere with the first optical system 31.

The single optical element 33 has the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The reflection surface, the first transmissive surface, and the second transmissive surface are therefore disposed with improved precision as compared, for example, with a case where the reflection surface is provided on a member different from the optical element having the first transmissive surface and the second transmissive surface.

In the present example, the reflection surface 41 is a concave curved surface. The projection system can therefore have a short focal length.

Further, in the present example, the optical element 33 has the convex second transmissive surface 43 protruding toward the enlargement side. An increase in the size of the reflection surface 41, which is located at the enlargement side of the intermediate image 35, can therefore be suppressed even when the projection distance is shortened. That is, the second transmissive surface 43 can refract the light flux and can therefore suppress inclination of the intermediate image 35, which is conjugate with the screen S, with respect to the second optical axis M of the reflection surface 41 and the resultant increase in the size of the intermediate image 35. An increase in the size of the reflection surface 41, which is located at the enlargement side of the intermediate image 35, can therefore be suppressed.

Moreover, in the present example, the optical element 33 has the convex first transmissive surface 42 protruding toward the enlargement side. An increase in the size of the reflection surface 41, which is located at the enlargement side of the intermediate image 35, is therefore readily suppressed even when the projection distance is shortened. That is, the first transmissive surface 42 can refract the light flux and can therefore suppress inclination of the intermediate image 35, which is conjugate with the screen S, with respect to the second optical axis M of the reflection surface 41 and the resultant increase in the size of the intermediate image 35. An increase in the size of the reflection surface 41, which is located at the enlargement side of the intermediate image 35, can therefore be suppressed.

In the optical element 33 in the present example, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43, which are located at the enlargement side of the intermediate image 35, are each an aspheric surface. Occurrence of aberrations is therefore readily suppressed in the enlargement-side image formation plane.

Further, the pupil P of the second optical system 32 inclines with respect to the imaginary vertical line V perpendicular to the second optical axis M of the reflection surface 41. A decrease in the amount of light at a periphery of the screen S that is the periphery at the upper side Y1 can therefore be suppressed as compared with a case where the pupil P of the second optical system 32 is parallel to the imaginary vertical line V. That is, in the configuration in which the pupil P inclines with respect to the imaginary vertical line V perpendicular to the second optical axis M, the amount of light flux F1, which reaches the upper portion of the screen S, increases as compared with the case where the pupil P is parallel to the imaginary vertical line V. Further, when the amount of light flux F1, which reaches the upper portion of the screen S, increases, the difference in the amount of light between the light flux F1 and the light flux F3, which reaches the lower portion of the screen S decreases. A decrease in the amount of light at the upper periphery of the screen S as compared with that at the lower periphery of the screen S can therefore be suppressed.

FIG. 5 shows the enlargement-side MTF of the projection system 3A. The horizontal axis of FIG. 5, which shows the MTF, represents the spatial frequency. The vertical axis of FIG. 5 represents a contrast reproduction ratio. In FIG. 5, the black graphs represent tangential light rays (T), and the gray graphs represent radial light rays (R). Out of the tangential light rays (T) and the radial light rays (R), the solid lines represent the light flux F1, the longest-line-segment broken lines represent the light flux F2, the long-line-segment broken lines represent the light flux F3, and the broken lines represent the light flux F4. The projection system 3A according to the present example provides high resolution, as shown in FIG. 5.

Example 2

FIG. 6 is a light ray diagram diagrammatically showing the entire projection system according to Example 2. FIG. 6 diagrammatically shows the light fluxes F1 to F4, which exit out of a projection system 3B according to the present example and reach the screen S. The light flux F1 is a light flux that reaches a smallest image height position. The light flux F4 is a light flux that reaches a largest image height position. The light fluxes F2 and F3 are light fluxes that reach positions between the position that the light flux F1 reaches and the position that the light flux F4 reaches. FIG. 7 is a light ray diagram of the projection system 3B according to Example 2. FIG. 8 is a light ray diagram of the second optical system 32 in Example 2.

The projection system according to Example 2 is based on the projection system according to Example 1, and the first optical system in Example 2 includes first and second deflectors that deflect the optical path of the first optical system. The projection system 3B according to the present example includes the first optical system 31 and the second optical system 32 sequentially arranged from the reduction side toward the enlargement side, as shown in FIG. 6. The first optical system 31 is a refractive optical system including a plurality of lenses. The second optical system 32 includes the optical element 33 and the reflector 34. The optical element 33 has the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The reflector 34 is a flat mirror. In the second optical system 32, the reflection surface 41, the reflector 34, the first transmissive surface 42, and the second transmissive surface 43 are located in the presented order along the light traveling direction from the reduction side toward the enlargement side.

The liquid crystal panels 18 of the image formation section 2 are disposed in the reduction-side image formation plane of the projection system 3B. The liquid crystal panels 18 form the projection images at one side of the first optical axis N of the first optical system 31 in a plane perpendicular to the first optical axis N. The screen S is disposed in the enlargement-side image formation plane of the projection system. The intermediate image 35 conjugate with the reduction-side image formation plane is formed between the first optical system 31 and the reflection surface 41 of the optical element 33. The intermediate image 35 is conjugate also with the enlargement-side image formation plane. The intermediate image 35 is formed at the side opposite the screen S with respect to the first optical axis N of the first optical system 31.

The first optical axis N of the first optical system 31 extends in the axis-Z direction in the present example. FIGS. 6, 7, and 8 are each a light ray diagram in the plane YZ. The liquid crystal panels 18 form the projection images at the upper side Y1 of the first optical axis N of the first optical system 31. The intermediate image 35 is formed at the lower side Y2 of the first optical axis N of the first optical system 31. The screen S is disposed at the upper side Y1 of the first optical axis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15 lenses L1 to L15, as shown in FIG. 7. The lenses L1 to L15 are arranged in the presented order from the reduction side toward the enlargement side. In the present example, the lenses L2 and L3 are bonded to each other into the first doublet L21. The lenses L4 and L5 are bonded to each other into the second doublet L22. The lenses L11 and L12 are bonded to each other into the third doublet L23. The lenses L13 and L14 are bonded to each other into the fourth doublet L24. The aperture O is disposed between the lens L8 and the lens L9.

The first optical system 31 includes the first deflector 38 and the second deflector 39, which deflect the optical path of the first optical system 31. The first deflector 38 and the second deflector 39 are each a flat mirror. The first deflector 38 is disposed adjacent to and at the reduction side of the aperture O. That is, the first deflector 38 is disposed between the lens L7 and the lens L8. The second deflector 39 is shifted from the aperture O toward the enlargement side. That is, the second deflector 39 is disposed between the lens L10 and the lens L11. The first optical axis N of the first optical system 31 is divided into a first section N1 of the first optical axis that is the section at the reduction side of the first deflector 38, a second section N2 of the first optical axis that is the section at the enlargement side of the first deflector 38 but up to the second deflector 39, and a third section N3 of the first optical axis that is the section at the enlargement side of the second deflector 39, and the angle between the first section N1 of the first optical axis and the second section N2 of the first optical axis is 90°. The angle between the second section N2 of the first optical axis and the third section N3 of the first optical axis is 90°. The first section N1 of the first optical axis and the third section N3 of the first optical axis are parallel to each other. In the present example, the first section N1 of the first optical axis and the third section N3 of the first optical axis extend in parallel to each other.

That is, the first deflector 38 is so disposed as to incline by 45° with respect to the first section N1 of the first optical axis and deflects the light flux in the first optical system 31 by 90° toward the upper side Y1. The second deflector 39 is so disposed as to incline by 45° with respect to the second section N2 of the first optical axis and deflects back the light flux in the first optical system 31 by 180°.

The optical element 33 includes the meniscus lens 36, which has a convex shape at the enlargement side, and the reflection coating layer 37, which is provided on part of the reduction-side surface of the meniscus lens 36. The reflection surface 41 of the optical element 33 is the reflection coating layer 37. The optical element 33 is designed by using the second optical axis M of the reflection surface 41 as the axis in the design stage. In other words, the second optical axis M is the design-stage optical axis of the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The second optical axis M of the reflection surface 41 coincides with the first optical axis N of the first optical system 31. The second optical axis M of the reflection surface 41 coincides with the third section N3 of the first optical axis N of the first optical system 31, as shown in FIG. 8. The second optical axis M of the reflection surface 41 therefore extends along the axis Z. The reflection surface 41 is located at the lower side Y2 of the second optical axis M. The first transmissive surface 42 and the second transmissive surface 43 are located at the upper side Y1 of the second optical axis M. The reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43 of the optical element 33 are each an aspheric surface. The aspheric surfaces are each a free-form surface in some cases. Also in this case, the free-form surfaces are designed by using the second optical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of the reflection surface 41. The reflector 34 is located at the upper side Y1 of the second optical axis M of the reflection surface 41. The reflector 34 is shifted from the optical element 33 toward the first optical system 31 in the direction along the second optical axis M of the reflection surface 41.

The pupil P of the second optical system 32 is located inside the second optical system 32. The pupil P of the second optical system 32 in the plane YZ is defined by the line that connects the upper intersection 53, where the upper peripheral light ray 51 a of the upper end light flux 51 passing through the axis-Y-direction upper end of the effective light ray range of the second transmissive surface 43 and the upper peripheral light ray 52 a of the lower end light flux 52 passing through the axis-Y-direction lower end of the effective light ray range 50 intersect each other in the plane YZ, to the lower intersection 54, where the lower peripheral light ray 51 b of the upper end light flux 51 and the lower peripheral light ray 52 b of the lower end light flux 52 intersect each other in the plane YZ. The pupil P is formed between the reflector 34 and the second transmissive surface 43. The pupil P inclines with respect to the imaginary vertical line V perpendicular to the second optical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3B are listed below. The surfaces of the lenses are numbered sequentially from the reduction side toward the enlargement side. Reference characters are given to the lenses, the first deflector, the second deflector, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface. Data labeled with a surface number that does not correspond to any of the lenses, the first deflector, the second deflector, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface is dummy data. Reference character R denotes the radius of curvature. Reference character D denotes the axial inter-surface distance. Reference character C denotes the aperture radius. Reference characters R, D, and C are each expressed in millimeters.

Reference Surface Refraction/ character number Shape R D Glass material reflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1 Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity 25.9100 SBSL7_OHARA Refraction 13.1294 3 Spherical Infinity 0.2000 Refraction 15.6811 L1 4 Spherical 28.2094 8.9572 463480.6806 Refraction 16.5145 5 Spherical −83.1544 0.2000 Refraction 16.2563 L2 6 Spherical 33.5314 6.6630 453456.8225 Refraction 14.7095 L3 7 Spherical −78.1478 1.2000 2.0010:29.132 Refraction 14.0000 8 Spherical 29.7884 0.2000 Refraction 13.4642 L4 9 Spherical 28.1457 9.6926 469236.8323 Refraction 13.6582 L5 10 Spherical −22.5231 1.2000 2.0009:29.135 Refraction 13.7136 11 Spherical −186.9823 0.2000 Refraction 14.8724 L6 12 Aspheric 48.9604 3.0063 441964.8821 Refraction 16.1663 13 Aspheric 314.2727 0.2000 Refraction 16.3015 L7 14 Spherical 81.4934 6.3039 469050.7791 Refraction 16.5299 15 Spherical −55.3604 19.1151 Refraction 16.7970 O 16 Spherical Infinity 0.0000 Reflection 26.4292 17 Spherical Infinity −19.1151 Refraction 17.8529 18 Spherical Infinity −0.2000 Refraction 19.1152 L8 19 Spherical −61.1427 −6.0716 2.0015:19.408 Refraction 19.3498 20 Spherical 196.5322 −0.8207 Refraction 19.0863 21 Spherical Infinity −18.2327 Refraction 18.3967 L9 22 Aspheric 27.0027 −1.6345 2.0027:19.317 Refraction 16.8350 23 Aspheric 187.7066 −0.2000 Refraction 18.3329  L10 24 Spherical −75.7408 −10.1959 590410.3496 Refraction 20.2617 25 Spherical 42.1350 −22.3002 Refraction 20.7008 26 Spherical Infinity 0.0000 Reflection 29.5422 27 Spherical Infinity 22.3002 Refraction 21.4652  L11 28 Spherical 35.1039 12.8742 437001.951 Refraction 22.3001  L12 29 Spherical −189.1707 3.8133 2.0010:29.134 Refraction 21.5043 30 Spherical 43.8798 0.2000 Refraction 20.3055  L13 31 Spherical 34.2291 17.9986 437001.951 Refraction 21.1074  L14 32 Spherical −85.4978 8.4736 792469.4538 Refraction 20.6876 33 Spherical 57.3732 9.8162 Refraction 20.8208  L15 34 Aspheric −226.8989 6.3040 ‘Z-E48R’ Refraction 21.3828 35 Aspheric −485.2593 0.2000 Refraction 22.3000 36 Spherical Infinity 1.5000 Refraction 26.7876 37 Spherical Infinity 40.2264 Refraction 27.6086 41 38 Aspheric −35.1906 0.0000 Reflection 38.8998 39 Spherical Infinity −40.2264 Refraction 74.5214 34 40 Spherical Infinity 0.0000 Reflection 30.0529 41 Spherical Infinity 40.2264 Refraction 30.0529 42 Spherical Infinity 0.0000 Refraction 107.4634 42 43 Aspheric −28.7213 1.2000 ‘Z-E48R’ Refraction 39.8330 43 44 Aspheric −42.6321 0.0000 Refraction 54.0576 45 Spherical Infinity 439.4195 Refraction 144.9591 S 46 Spherical Infinity 0.0000 Refraction 1488.5481

The aspheric coefficients of each of the aspheric surfaces are listed below.

Surface number S12 S13 S22 Radius of 48.96044013 314.2727343 27.00272101 curvature in axis-Y direction Conic constant 1.568 −1.3 −1 (k) Fourth-order −1.02602E−05 3.23749E−06 −7.77232E−07 coefficient (A) Sixth-order 2.22500E−08 2.10974E−08 −2.87978E−09 coefficient (B) Eighth-order −4.11479E−11 −4.06491E−11 −3.62426E−12 coefficient (C) Tenth-order 2.28527E−13 2.41451E−13 coefficient (D) Twelfth-order coefficient (E) Fourteenth-order coefficient (F) Surface number S23 S34 S35 Radius of 187.7066332 −226.8988513 −485.2592728 curvature in axis-Y direction Conic constant −0.88 90 0 (k) Fourth-order −7.79758E−06 −4.00626E−05 −7.89993E−05 coefficient (A) Sixth-order 1.61670E−09 1.42410E−07 2.15938E−07 coefficient (B) Eighth-order −2.71849E−12 −3.51878E−10 −4.26635E−10 coefficient (C) Tenth-order 5.84931E−13 5.81509E−13 coefficient (D) Twelfth-order −7.00335E−16 −6.28266E−16 coefficient (E) Fourteenth-order 4.42366E−19 3.57966E−19 coefficient (F) Surface number S38 S43 S44 Radius of −35.19059003 −28.72125677 −42.63205393 curvature in axis-Y direction Conic constant −1.65124531 −2.48275343 −0.82812574 (k) Fourth-order −1.44803E−07 −6.52555E−06 1.63369E−06 coefficient (A) Sixth-order −3.34034E−10 −2.02478E−09 −1.36041E−10 coefficient (B) Eighth-order 1.23576E−13 2.29963E−12 −4.47648E−14 coefficient (C) Tenth-order −5.90820E−17 3.72271E−17 coefficient (D) Twelfth-order 8.23282E−21 −3.16121E−19 coefficient (E) Fourteenth-order −5.47662E−25 −7.45167E−23 coefficient (F)

The maximum object height, the numerical aperture, the mirror radius, the lens overall length, and TR of the projection system 3B are as follows: The maximum object height is the dimension from the first optical axis N of the projection system 3B to the farthest point therefrom in the image formation region of the surface of each of the liquid crystal panels 18. The maximum object height is expressed in millimeters. The numerical aperture is abbreviated to NA. The mirror radius is the radius of the first reflection surface in millimeters. The final lens radius is the lens radius of the second transmissive surface in millimeters. The lens overall length of the projection system 3B is the distance in millimeters from the liquid crystal panels 18 to the second transmissive surface in the axis-Z direction. TR stands for the throw ratio and is the quotient of the operation of dividing the projection distance by the axis-X-direction dimension of a projection image projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 38.9 Final lens radius 54.1 Lens overall length 295 TR (0.59″WXGA) 0.270

Effects and Advantages

The projection system according to the present example can provide the same effects and advantages as those provided by the projection system according to Example 1. In the present example, in which the first and second deflectors are provided, the optical path of the first optical system is deflected back. The area occupied by the first optical system can therefore be reduced when viewed along the axis-Y direction, that is, when taken along the plane XZ.

FIG. 9 shows the enlargement-side MTF of the projection system 3B. The projection system 3B according to the present example provides high resolution, as shown in FIG. 9.

Example 3

FIG. 10 is a light ray diagram diagrammatically showing the entirety of a projection system 3C according to Example 3. FIG. 10 diagrammatically shows the light fluxes F1 to F4, which exit out of the projection system 3C according to the present example and reach the screen S. The light flux F1 is a light flux that reaches a smallest image height position. The light flux F4 is a light flux that reaches a largest image height position. The light fluxes F2 and F3 are light fluxes that reach positions between the position that the light flux F1 reaches and the position that the light flux F4 reaches. FIG. 11 is a light ray diagram of the projection system 3C according to Example 3. FIG. 12 is a light ray diagram of the second optical system.

The projection system 3C according to the present example includes the first optical system 31 and the second optical system 32 sequentially arranged from the reduction side toward the enlargement side, as shown in FIG. 11. The first optical system 31 is a refractive optical system including a plurality of lenses. The second optical system 32 includes the optical element 33 and the reflector 34. The optical element 33 has a light-incident-side transmissive surface 44, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The reflector 34 is a flat mirror. In the second optical system 32, the light-incident-side transmissive surface 44, the reflection surface 41, the light-incident-side transmissive surface 44, the reflector 34, the first transmissive surface 42, and the second transmissive surface 43 are located in the presented order along the light traveling direction from the reduction side toward the enlargement side.

The liquid crystal panels 18 of the image formation section 2 are disposed in the reduction-side image formation plane of the projection system 3C. The liquid crystal panels 18 form the projection images at one side of the first optical axis N of the first optical system 31 in a plane perpendicular to the first optical axis N. The screen S is disposed in the enlargement-side image formation plane of the projection system. The intermediate image 35 conjugate with the reduction-side image formation plane is formed between the first optical system 31 and the reflection surface 41 of the optical element 33. The intermediate image 35 is conjugate also with the enlargement-side image formation plane. The intermediate image 35 is formed at the side opposite the screen S with respect to the first optical axis N of the first optical system 31.

The first optical axis N of the first optical system 31 extends in the axis-Z direction in the present example. FIGS. 10, 11, and 12 are each a light ray diagram in the plane YZ. The liquid crystal panels 18 form the projection images at the upper side Y1 of the first optical axis N of the first optical system 31. The intermediate image 35 is formed at the lower side Y2 of the first optical axis N of the first optical system 31. The screen S is disposed at the upper side Y1 of the first optical axis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15 lenses L1 to L15, as shown in FIG. 11. The lenses L1 to L15 are arranged in the presented order from the reduction side toward the enlargement side. In the present example, the lenses L2 and L3 are bonded to each other into the first doublet L21. The lenses L4 and L5 are bonded to each other into the second doublet L22. The lenses L11 and L12 are bonded to each other into the third doublet L23. The lenses L13 and L14 are bonded to each other into the fourth doublet L24. The aperture O is disposed between the lens L7 and the lens L8.

The optical element 33 includes the meniscus lens 36, which has a convex shape at the enlargement side, and the reflection coating layer 37, which is provided on part of the enlargement-side surface of the meniscus lens 36. The reflection surface 41 of the optical element 33 is the reflection coating layer 37. The optical element 33 is designed by using the second optical axis M of the reflection surface 41 as the axis in the design stage. In other words, the second optical axis M is the design-stage optical axis of the light-incident-side transmissive surface 44, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The second optical axis M of the reflection surface 41 coincides with the first optical axis N of the first optical system 31, as shown in FIG. 12. The second optical axis M of the reflection surface 41 therefore extends along the axis Z. The light-incident-side transmissive surface 44 and the reflection surface 41 are located at the lower side Y2 of the second optical axis M. The first transmissive surface 42 and the second transmissive surface 43 are located at the upper side Y1 of the second optical axis. The light-incident-side transmissive surface 44, and the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43 of the optical element 33 are each an aspheric surface. The aspheric surfaces are each a free-form surface in some cases. Also in this case, the free-form surfaces are designed by using the second optical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of the reflection surface 41. The reflector 34 is located at the upper side Y1 of the second optical axis M of the reflection surface 41. The reflector 34 is shifted from the optical element 33 toward the first optical system 31 in the direction along the second optical axis M of the reflection surface 41.

The pupil P of the second optical system 32 is located inside the second optical system 32. The pupil P of the second optical system 32 in the plane YZ is defined by the line that connects the upper intersection 53, where the upper peripheral light ray 51 a of the upper end light flux 51 passing through the axis-Y-direction upper end of the effective light ray range of the second transmissive surface 43 and the upper peripheral light ray 52 a of the lower end light flux 52 passing through the axis-Y-direction lower end of the effective light ray range 50 intersect each other in the plane YZ, to the lower intersection 54, where the lower peripheral light ray 51 b of the upper end light flux 51 and the lower peripheral light ray 52 b of the lower end light flux 52 intersect each other in the plane YZ. The pupil P is formed between the reflector 34 and the second transmissive surface 43. The pupil P inclines with respect to the imaginary vertical line V perpendicular to the second optical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3C are listed below. The surfaces of the lenses are numbered sequentially from the reduction side toward the enlargement side. Reference characters are given to the lenses, the light-incident-side projection surface, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface. Data labeled with a surface number that does not correspond to any of the lenses, the light-incident-side projection surface, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface is dummy data. Reference character R denotes the radius of curvature. Reference character D denotes the axial inter-surface distance. Reference character C denotes the aperture radius. Reference characters R, D, and C are each expressed in millimeters.

Reference Surface Refraction/ character number Shape R D Glass material reflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1 Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity 25.9100 SBSL7_OHARA Refraction 13.6097 3 Spherical Infinity 0.0000 Refraction 17.0021 L1 4 Spherical 41.2144 9.8241 SFPL51_OHARA Refraction 17.8162 5 Spherical −43.6282 0.2000 Refraction 17.7483 L2 6 Spherical 23.5357 6.2884 SFSL5_OHARA Refraction 14.9123 L3 7 Spherical 94.8272 1.2000 STIH6_OHARA Refraction 14.0000 8 Spherical 21.4819 0.2000 Refraction 12.6277 L4 9 Spherical 19.0505 10.4909 SBSL7_OHARA Refraction 12.6034 L5 10 Spherical −21.2275 1.2000 TAFD25_HOYA Refraction 12.0117 11 Spherical 63.5114 1.0411 Refraction 11.6290 L6 12 Aspheric 49.0884 1.2000 LBAL35_OHARA Refraction 11.6454 13 Aspheric 27.0575 0.2000 Refraction 11.6632 L7 14 Spherical 26.8149 7.0725 SFSL5_OHARA Refraction 11.9375 15 Spherical −32.5544 4.3889 Refraction 11.9390 O 16 Spherical Infinity 2.5976 Refraction 10.7320 L8 17 Spherical 45.3300 7.0474 STIH53_OHARA Refraction 12.3109 18 Spherical −35.8311 0.2000 Refraction 12.4566 L9 19 Aspheric −56.8046 1.5968 LLAM60_OHARA Refraction 12.3293 20 Aspheric 24.3773 7.4673 Refraction 12.6338 21 Spherical Infinity 2.8159 Refraction 14.9857  L10 22 Spherical 33.2956 4.5985 STIM22_OHARA Refraction 20.1790 23 Spherical 49.7914 17.6365 Refraction 20.0451  L11 24 Spherical 45.3688 20.9746 STIM2_OHARA Refraction 26.0000  L12 25 Spherical −28.7126 1.2000 STIH6_OHARA Refraction 23.5216 26 Spherical 115.5270 0.2000 Refraction 24.2345  L13 27 Spherical 33.8126 15.5800 STIL25_OHARA Refraction 27.3836  L14 28 Spherical 899.1542 1.2000 STIH6_OHARA Refraction 26.7372 29 Spherical 42.8200 7.9678 Refraction 24.3547  L15 30 Aspheric −256.9466 10.0000 ‘Z-E48R’ Refraction 24.5227 31 Aspheric 76.1015 7.8140 Refraction 21.8030 32 Spherical Infinity 1.7043 Refraction 21.8850 33 Spherical Infinity 26.6661 Refraction 22.7703 44 34 Aspheric −53.7754 4.0174 ‘Z-E48R’ Refraction 30.1927 41 35 Aspheric −37.0708 −4.0174 ‘Z-E48R’ Reflection 31.6638 44 36 Aspheric −53.7754 −26.6661 Refraction 29.5984 34 37 Spherical Infinity 0.0000 Reflection 42.8206 38 Spherical Infinity 26.6606 Refraction 42.8206 39 Spherical Infinity 0.0000 Refraction 110.7647 42 40 Aspheric −61.4764 4.0174 ‘Z-E48R’ Refraction 43.5854 43 41 Aspheric −200.8496 0.0000 Refraction 59.9999 42 Spherical Infinity 439.4195 Refraction 131.0019 S 43 Spherical Infinity 0.0000 Refraction 1454.8316

The aspheric coefficients of each of the aspheric surfaces are listed below.

Surface number S12 S13 S19 S20 Radius of 49.08839049 27.05749563 −56.80463531 24.37733913 curvature in axis-Y direction Conic constant 1.568 −1.3 −1 −0.88 (k) Fourth-order −1.27624E−04 −9.62452E−05 −2.35727E−05 −5.71363E−06 coefficient (A) Sixth-order 6.79968E−07 7.36058E−07 −6.95764E−09 −9.06493E−09 coefficient (B) Eighth-order −1.49344E−09 −2.04610E−09 −2.33118E−11 −1.65962E−11 coefficient (C) Tenth-order 2.18051E−12 3.01616E−12 coefficient (D) Twelfth-order coefficient (E) Fourteenth-order coefficient (F) Surface number S30 S31 S34 S35 Radius of −256.9466198 76.10151145 −53.77538203 −37.0707934 curvature in axis-Y direction Conic constant 90 0 1.432637618 −1 (k) Fourth-order 3.81759E−05 −2.49871E−05 −7.27509E−06 1.95126E−07 coefficient (A) Sixth-order −2.36256E−08 1.46370E−07 1.22445E−08 −2.56458E−09 coefficient (B) Eighth-order −2.04848E−11 −2.70415E−10 −8.06489E−12 2.98409E−12 coefficient (C) Tenth-order 6.55740E−14 2.57801E−13 7.19014E−15 6.07298E−16 coefficient (D) Twelfth-order −4.72334E−17 −2.07333E−16 −8.05971E−18 −3.51995E−18 coefficient (E) Fourteenth-order 3.01373E−20 2.90536E−19 2.85331E−21 1.46175E−21 coefficient (F) Surface number S36 S40 S41 Radius of −53.77538203 −61.47639674 −200.8496205 curvature in axis-Y direction Conic constant 1.432637618 −0.946487863 8.952212348 (k) Fourth-order −7.27509E−06 −3.81258E−06 −9.72802E−07 coefficient (A) Sixth-order 1.22445E−08 2.37350E−09 2.00223E−10 coefficient (B) Eighth-order −8.06489E−12 −1.02258E−12 −4.09223E−14 coefficient (C) Tenth-order 7.19014E−15 coefficient (D) Twelfth-order −8.05971E−18 coefficient (E) Fourteenth-order 2.85331E−21 coefficient (F)

The maximum object height, the numerical aperture, the mirror radius, the lens overall length, and TR of the projection system 3C are as follows: The maximum object height is the dimension from the first optical axis N of the projection system 3C to the farthest point therefrom in the image formation region of the surface of each of the liquid crystal panels 18. The maximum object height is expressed in millimeters. The numerical aperture is abbreviated to NA. The mirror radius is the radius of the first reflection surface in millimeters. The final lens radius is the lens radius of the second transmissive surface in millimeters. The lens overall length of the projection system 3C is the distance in millimeters from the liquid crystal panels 18 to the second transmissive surface in the axis-Z direction. TR stands for the throw ratio and is the quotient of the operation of dividing the projection distance by the axis-X-direction dimension of a projection image projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 31.7 Final lens radius 60.0 Lens overall length 220 TR (0.59″WXGA) 0.27

Effects and Advantages

The projection system according to the present example can provide the same effects and advantages as those provided by the projection system according to Example 1.

In the present example, the light-incident-side transmissive surface 44 can refract the light flux incident on the reflection surface 41 and the light flux reflected off the reflection surface 41 in the second optical system 32. The projection distance of the projection system can therefore be further shortened as compared with the case where the second optical system 32 has the first transmissive surface 42 and the second transmissive surface 43.

Since the light-incident-side transmissive surface 44, which is located at the enlargement side of the intermediate image 35, is an aspheric surface, occurrence of aberrations is readily suppressed in the enlargement-side image formation plane.

FIG. 13 shows the enlargement-side MTF of the projection system 3C. The projection system 3C according to the present example provides high resolution, as shown in FIG. 13.

Example 4

FIG. 14 is a light ray diagram diagrammatically showing the entirety of a projection system 3D according to Example 4. FIG. 14 diagrammatically shows the light fluxes F1 to F4, which exit out of the projection system 3D according to the present example and reach the screen S. The light flux F1 is a light flux that reaches a smallest image height position. The light flux F4 is a light flux that reaches a largest image height position. The light fluxes F2 and F3 are light fluxes that reach positions between the position that the light flux F1 reaches and the position that the light flux F4 reaches. FIG. 15 is a light ray diagram of the projection system 3D according to Example 4. FIG. 16 is a light ray diagram of the second optical system in Example 4.

The projection system according to Example 4 is based on the projection system according to Example 3, and the first optical system in Example 4 includes first and second deflectors that deflect the optical path of the first optical system. The projection system 3D according to the present example includes the first optical system 31 and the second optical system 32 sequentially arranged from the reduction side toward the enlargement side, as shown in FIG. 15. The first optical system 31 is a refractive optical system including a plurality of lenses. The second optical system 32 includes the optical element 33 and the reflector 34. The optical element 33 has the light-incident-side transmissive surface 44, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The reflector 34 is a flat mirror. In the second optical system 32, the light-incident-side transmissive surface 44, the reflection surface 41, the light-incident-side transmissive surface 44, the reflector 34, the first transmissive surface 42, and the second transmissive surface 43 are located in the presented order along the light traveling direction from the reduction side toward the enlargement side.

The liquid crystal panels 18 of the image formation section 2 are disposed in the reduction-side image formation plane of the projection system 3D. The liquid crystal panels 18 form the projection images at one side of the first optical axis N of the first optical system 31 in a plane perpendicular to the first optical axis N. The screen S is disposed in the enlargement-side image formation plane of the projection system. The intermediate image 35 conjugate with the reduction-side image formation plane is formed between the first optical system 31 and the reflection surface 41 of the optical element 33. The intermediate image 35 is conjugate also with the enlargement-side image formation plane. The intermediate image 35 is formed at the side opposite the screen S with respect to the first optical axis N of the first optical system 31.

The first optical axis N of the first optical system 31 extends in the axis-Z direction in the present example. FIGS. 14, 15, and 16 are each a light ray diagram in the plane YZ. The liquid crystal panels 18 form the projection images at the upper side Y1 of the first optical axis N of the first optical system 31. The intermediate image 35 is formed at the lower side Y2 of the first optical axis N of the first optical system 31. The screen S is disposed at the upper side Y1 of the first optical axis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15 lenses L1 to L15, as shown in FIG. 15. The lenses L1 to L15 are arranged in the presented order from the reduction side toward the enlargement side. In the present example, the lenses L2 and L3 are bonded to each other into the first doublet L21. The lenses L4 and L5 are bonded to each other into the second doublet L22. The lenses L11 and L12 are bonded to each other into the third doublet L23. The lenses L13 and L14 are bonded to each other into the fourth doublet L24. The aperture O is disposed between the lens L8 and the lens L9.

The first optical system 31 includes the first deflector 38 and the second deflector 39, which deflect the optical path of the first optical system 31. The first deflector 38 and the second deflector 39 are each a flat mirror. The first deflector 38 is disposed adjacent to and at the reduction side of the aperture O. That is, the first deflector 38 is disposed between the lens L7 and the lens L8. The second deflector 39 is shifted from the aperture O toward the enlargement side. That is, the second deflector 39 is disposed between the lens L10 and the lens L11. The first optical axis N of the first optical system 31 is divided into the first section N1 of the first optical axis that is the section at the reduction side of the first deflector 38, the second section N2 of the first optical axis that is the section at the enlargement side of the first deflector 38 but up to the second deflector 39, and the third section N3 of the first optical axis that is the section at the enlargement side of the second deflector 39, and the angle between the first section N1 of the first optical axis and the second section N2 of the first optical axis is 90°. The angle between the second section N2 of the first optical axis and the third section N3 of the first optical axis is 90°. The first section N1 of the first optical axis and the third section N3 of the first optical axis are parallel to each other. In the present example, the first section N1 of the first optical axis and the third section N3 of the first optical axis extend in parallel to each other.

That is, the first deflector 38 is so disposed as to incline by 45° with respect to the first section N1 of the first optical axis and deflects the light flux in the first optical system 31 by 90° toward the upper side Y1. The second deflector 39 is so disposed as to incline by 45° with respect to the second section N2 of the first optical axis and deflects back the light flux in the first optical system 31 by 180°.

The optical element 33 includes the meniscus lens 36, which has a convex shape at the enlargement side, and the reflection coating layer 37, which is provided on part of the enlargement-side surface of the meniscus lens 36. The reflection surface 41 of the optical element 33 is the reflection coating layer 37. The optical element 33 is designed by using the second optical axis M of the reflection surface 41 as the axis in the design stage. In other words, the second optical axis M is the design-stage optical axis of the light-incident-side transmissive surface 44, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The second optical axis M of the reflection surface 41 coincides with the third section N3 of the first optical axis N of the first optical system 31, as shown in FIG. 16. The second optical axis M of the reflection surface 41 therefore extends along the axis Z. The light-incident-side transmissive surface 44 and the reflection surface 41 are located at the lower side Y2 of the second optical axis M. The first transmissive surface 42 and the second transmissive surface 43 are located at the upper side Y1 of the second optical axis M. The light-incident-side transmissive surface 44, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43 of the optical element 33 are each an aspheric surface. The aspheric surfaces are each a free-form surface in some cases. Also in this case, the free-form surfaces are designed by using the second optical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of the reflection surface 41. The reflector 34 is located at the upper side Y1 of the second optical axis M of the reflection surface 41. The reflector 34 is shifted from the optical element 33 toward the first optical system 31 in the direction along the second optical axis M of the reflection surface 41.

The pupil P of the second optical system 32 is located inside the second optical system 32. The pupil P of the second optical system 32 in the plane YZ is defined by the line that connects the upper intersection 53, where the upper peripheral light ray 51 a of the upper end light flux 51 passing through the axis-Y-direction upper end of the effective light ray range of the second transmissive surface 43 and the upper peripheral light ray 52 a of the lower end light flux 52 passing through the axis-Y-direction lower end of the effective light ray range 50 intersect each other in the plane YZ, to the lower intersection 54, where the lower peripheral light ray 51 b of the upper end light flux 51 and the lower peripheral light ray 52 b of the lower end light flux 52 intersect each other in the plane YZ. The pupil P is formed between the reflector 34 and the second transmissive surface 43. The pupil P inclines with respect to the imaginary vertical line V perpendicular to the second optical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3D are listed below. The surfaces of the lenses are numbered sequentially from the reduction side toward the enlargement side. Reference characters are given to the lenses, the first deflector, the second deflector, the light-incident-side projection surface, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface. Data labeled with a surface number that does not correspond to any of the lenses, the first deflector, the second deflector, the light-incident-side projection surface, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface is dummy data. Reference character R denotes the radius of curvature. Reference character D denotes the axial inter-surface distance. Reference character C denotes the aperture radius. Reference characters R, D, and C are each expressed in millimeters.

Reference Surface Refraction/ character number Shape R D Glass material reflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1 Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity 25.9100 SBSL7_OHARA Refraction 13.1866 3 Spherical Infinity 0.2000 Refraction 15.8391 L1 4 Spherical 60.8192 8.3858 447472.8179 Refraction 16.2149 5 Spherical −33.6543 0.2000 Refraction 16.2525 L2 6 Spherical 42.1742 6.8398 449655.8302 Refraction 14.5611 L3 7 Spherical −44.7501 1.2000 2.0010:29.134 Refraction 14.0000 8 Spherical 43.1052 0.2000 Refraction 13.8696 L4 9 Spherical 31.6779 10.8169 447567.8304 Refraction 14.3070 L5 10 Spherical −21.9104 1.2000 2.0010:28.886 Refraction 14.3931 11 Spherical −58.3816 0.2000 Refraction 15.5371 L6 12 Aspheric 96.3261 3.0000 878827.3593 Refraction 16.3816 13 Aspheric 60.9753 0.2000 Refraction 16.4506 L7 14 Spherical 47.0513 9.2823 449491.8071 Refraction 16.8655 15 Spherical −47.2067 20.0299 Refraction 17.1995 O 16 Spherical Infinity 0.0000 Reflection 27.4865 17 Spherical Infinity −20.0299 Refraction 18.5462 18 Spherical Infinity −0.2000 Refraction 20.0401 L8 19 Spherical −57.0398 −5.8695 2.0027:19.317 Refraction 20.3345 20 Spherical 1094.6879 −1.8973 Refraction 20.0379 21 Spherical Infinity −19.0977 Refraction 19.3260 L9 22 Aspheric 50.6705 −1.2000 2.0027:19.317 Refraction 17.6192 23 Aspheric −202.8274 −0.2000 Refraction 18.2801  L10 24 Spherical −51.6804 −8.0027 652914.3585 Refraction 19.7819 25 Spherical 91.1078 −20.8653 Refraction 19.9676 26 Spherical Infinity 0.0000 Reflection 28.3233 27 Spherical Infinity 20.8653 Refraction 20.4211  L11 28 Spherical 38.7604 12.4568 614216.3226 Refraction 20.9520  L12 29 Spherical −45.7966 3.0000 2.0027:19.317 Refraction 20.6415 30 Spherical 47.4799 10.4635 Refraction 19.8139  L13 31 Spherical −92.5686 3.3996 611216.3189 Refraction 21.2199  L14 32 Spherical −56.0227 6.0607 675797.2751 Refraction 21.7046 33 Spherical −33.7704 0.2000 Refraction 22.3552  L15 34 Aspheric −243.3783 2.8440 ‘Z-E48R’ Refraction 22.3333 35 Aspheric 25.0399 9.7794 Refraction 20.3862 36 Spherical Infinity 1.5030 Refraction 20.4862 37 Spherical Infinity 26.6612 Refraction 21.1335 44 38 Aspheric −68.3577 4.2395 ‘Z-E48R’ Refraction 28.3267 41 39 Aspheric −38.4885 −4.2395 ‘Z-E48R’ Reflection 29.5616 44 40 Aspheric −68.3577 −26.6612 Refraction 27.6155 34 41 Spherical Infinity 0.0000 Reflection 33.2362 42 Spherical Infinity 26.6613 Refraction 33.2362 43 Spherical Infinity 0.0000 Refraction 92.9510 42 44 Aspheric −49.2660 4.2395 ‘Z-E48R’ Refraction 37.4399 43 45 Aspheric −147.0473 0.0000 Refraction 54.3569 46 Spherical Infinity 439.4195 Refraction 120.3501 S 47 Spherical Infinity 0.0000 Refraction 1458.6948

The aspheric coefficients of each of the aspheric surfaces are listed below.

Surface number S12 S13 S22 S23 Radius of 96.3260961 60.97528446 50.67048364 −202.8273751 curvature in axis-Y direction Conic constant 1.568 −1.3 −1 −0.88 (k) Fourth-order −1.00271E−05 −7.79867E−06 −7.72183E−07 −5.91829E−06 coefficient (A) Sixth-order 3.47797E−08 3.65406E−08 2.19648E−09 2.49647E−09 coefficient (B) Eighth-order −1.44942E−11 −2.65355E−11 −3.76843E−12 −3.70003E−12 coefficient (C) Tenth-order 5.15470E−15 2.45256E−14 coefficient (D) Twelfth-order coefficient (E) Fourteenth-order coefficient (F) Surface number S34 S35 S38 S39 Radius of −243.3783218 25.03986207 −68.35771811 −38.48848791 curvature in axis-Y direction Conic constant 90 0 3.309513291 −1 (k) Fourth-order 2.59808E−05 −3.57184E−05 −9.53327E−06 5.03313E−07 coefficient (A) Sixth-order 4.74275E−08 1.85049E−07 1.28167E−08 −5.25830E−09 coefficient (B) Eighth-order −3.01496E−10 −5.17448E−10 −1.14594E−11 8.21603E−12 coefficient (C) Tenth-order 6.68588E−13 5.85946E−13 1.49774E−14 −5.49356E−15 coefficient (D) Twelfth-order −7.34682E−16 −4.18133E−16 −1.53274E−17 4.32667E−19 coefficient (E) Fourteenth-order 4.02340E−19 4.30864E−19 5.55757E−21 3.62088E−22 coefficient (F) Surface number S40 S44 S45 Radius of −68.35771811 −49.26602456 −147.047343 curvature in axis-Y direction Conic constant 3.309513291 −13.20511972 5.099781969 (k) Fourth-order −9.53327E−06 −1.27110E−05 −8.98450E−07 coefficient (A) Sixth-order 1.28167E−08 7.61054E−09 1.15337E−10 coefficient (B) Eighth-order −1.14594E−11 −3.45915E−12 −3.33257E−14 coefficient (C) Tenth-order 1.49774E−14 coefficient (D) Twelfth-order −1.53274E−17 coefficient (E) Fourteenth-order 5.55757E−21 coefficient (F)

The maximum object height, the numerical aperture, the mirror radius, the lens overall length, and TR of the projection system 3D are as follows: The maximum object height is the dimension from the first optical axis N of the projection system 3D to the farthest point therefrom in the image formation region of the surface of each of the liquid crystal panels 18. The maximum object height is expressed in millimeters. The numerical aperture is abbreviated to NA. The mirror radius is the radius of the first reflection surface in millimeters. The final lens radius is the lens radius of the second transmissive surface in millimeters. The lens overall length of the projection system 3D is the distance in millimeters from the liquid crystal panels 18 to the second transmissive surface in the axis-Z direction. TR stands for the throw ratio and is the quotient of the operation of dividing the projection distance by the axis-X-direction dimension of a projection image projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 29.6 Final lens radius 54.4 Lens overall length 276 TR (0.59″WXGA) 0.275

Effects and Advantages

The projection system according to the present example can provide the same effects and advantages as those provided by the projection system according to Example 3. In the present example, in which the first and second deflectors are provided, the optical path of the first optical system is deflected back. The area occupied by the first optical system can therefore be reduced when viewed along the axis-Y direction.

FIG. 17 shows the enlargement-side MTF of the projection system 3D. The projection system 3D according to the present example provides high resolution, as shown in FIG. 17.

Example 5

FIG. 18 is a light ray diagram diagrammatically showing the entirety of a projection system 3E according to Example 5. FIG. 18 diagrammatically shows the light fluxes F1 to F4, which exit out of the projection system 3E according to the present example and reach the screen S. The light flux F1 is a light flux that reaches a smallest image height position. The light flux F4 is a light flux that reaches a largest image height position. The light fluxes F2 and F3 are light fluxes that reach positions between the position that the light flux F1 reaches and the position that the light flux F4 reaches. FIG. 19 is a light ray diagram of the projection system 3E according to Example 5. FIG. 20 is a light ray diagram of the second optical system in Example 5.

In the projection system according to Example 5, the first optical system includes first and second deflectors that deflect the optical path of the first optical system, as in Example 4. The projection system 3E according to the present example includes the first optical system 31 and the second optical system 32 sequentially arranged from the reduction side toward the enlargement side, as shown in FIG. 19. The first optical system 31 is a refractive optical system including a plurality of lenses. The second optical system 32 includes the optical element 33 and the reflector 34. The optical element 33 has the light-incident-side transmissive surface 44, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The reflector 34 is a flat mirror. In the second optical system 32, the light-incident-side transmissive surface 44, the reflection surface 41, the light-incident-side transmissive surface 44, the reflector 34, the first transmissive surface 42, and the second transmissive surface 43 are located in the presented order along the light traveling direction from the reduction side toward the enlargement side.

The liquid crystal panels 18 of the image formation section 2 are disposed in the reduction-side image formation plane of the projection system 3E. The liquid crystal panels 18 form the projection images at one side of the first optical axis N of the first optical system 31 in a plane perpendicular to the first optical axis N. The screen S is disposed in the enlargement-side image formation plane of the projection system. The intermediate image 35 conjugate with the reduction-side image formation plane is formed between the first optical system 31 and the reflection surface 41 of the optical element 33. The intermediate image 35 is conjugate also with the enlargement-side image formation plane. The intermediate image 35 is formed at the side opposite the screen S with respect to the first optical axis N of the first optical system 31.

The first optical axis N of the first optical system 31 extends in the axis-Z direction in the present example. FIGS. 18, 19, and 20 are each a light ray diagram in the plane YZ. The liquid crystal panels 18 form the projection images at the upper side Y1 of the first optical axis N of the first optical system 31. The intermediate image 35 is formed at the lower side Y2 of the first optical axis N of the first optical system 31. The screen S is disposed at the upper side Y1 of the first optical axis N of the first optical system 31.

The first optical system 31 includes the cross dichroic prism 19 and 15 lenses L1 to L15, as shown in FIG. 19. The lenses L1 to L15 are arranged in the presented order from the reduction side toward the enlargement side. In the present example, the lenses L2 and L3 are bonded to each other into the first doublet L21. The lenses L4 and L5 are bonded to each other into the second doublet L22. The lenses L11 and L12 are bonded to each other into the third doublet L23. The lenses L13 and L14 are bonded to each other into the fourth doublet L24. The lens 15 is a lens having no portion at the upper side Y1 of the first optical axis N of the first optical system 31. The aperture O is disposed between the lens L8 and the lens L9.

The first optical system 31 includes the first deflector 38 and the second deflector 39, which deflect the optical path of the first optical system 31. The first deflector 38 and the second deflector 39 are each a flat mirror. The first deflector 38 is disposed adjacent to and at the reduction side of the aperture O. That is, the first deflector 38 is disposed between the lens L7 and the lens L8. The second deflector 39 is shifted from the aperture O toward the enlargement side. That is, the second deflector 39 is disposed between the lens L10 and the lens L11. The first optical axis N of the first optical system 31 is divided into the first section N1 of the first optical axis that is the section at the reduction side of the first deflector 38, the second section N2 of the first optical axis that is the section at the enlargement side of the first deflector 38 but up to the second deflector 39, and the third section N3 of the first optical axis that is the section at the enlargement side of the second deflector 39, and the angle between the first section N1 of the first optical axis and the second section N2 of the first optical axis is 90°. The angle between the second section N2 of the first optical axis and the third section N3 of the first optical axis is 90°. The first section N1 of the first optical axis and the third section N3 of the first optical axis are parallel to each other. In the present example, the first section N1 of the first optical axis and the third section N3 of the first optical axis extend in parallel to each other.

That is, the first deflector 38 is so disposed as to incline by 45° with respect to the first section N1 of the first optical axis and deflects the optical path of the first optical system 31 by 90° toward the upper side Y1. The second deflector 39 is so disposed as to incline by 45° with respect to the second section N2 of the first optical axis and deflects back the light path of the first optical system 31 by 180°.

The optical element 33 includes the meniscus lens 36, which has a convex shape at the enlargement side, and the reflection coating layer 37, which is provided on part of the enlargement-side surface of the meniscus lens 36. The reflection surface 41 of the optical element 33 is the reflection coating layer 37. The optical element 33 is designed by using the second optical axis M of the reflection surface 41 as the axis in the design stage. In other words, the second optical axis M is the design-stage optical axis of the light-incident-side transmissive surface 44, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43. The second optical axis M of the reflection surface 41 coincides with the third section N3 of the first optical axis N of the first optical system 31, as shown in FIG. 20. The second optical axis M of the reflection surface 41 therefore extends along the axis Z. The light-incident-side transmissive surface 44 and the reflection surface 41 are located at the lower side Y2 of the second optical axis M. The first transmissive surface 42 and the second transmissive surface 43 are located at the upper side Y1 of the second optical axis M. The light-incident-side transmissive surface 44, the reflection surface 41, the first transmissive surface 42, and the second transmissive surface 43 of the optical element 33 are each an aspheric surface. The aspheric surfaces are each a free-form surface in some cases. Also in this case, the free-form surfaces are designed by using the second optical axis M as the design-stage axis.

The reflector 34 is perpendicular to the second optical axis M of the reflection surface 41. The reflector 34 is located at the upper side Y1 of the second optical axis M of the reflection surface 41. The reflector 34 is shifted from the optical element 33 toward the first optical system 31 in the direction along the second optical axis M of the reflection surface 41. The reflector 34 and the lens L15 of the first optical system 31 overlap with each other when viewed in the direction perpendicular to the first optical axis N of the first optical system 31.

The pupil P of the second optical system 32 is located inside the second optical system 32. The pupil P of the second optical system 32 in the plane YZ is defined by the line that connects the upper intersection 53, where the upper peripheral light ray 51 a of the upper end light flux 51 passing through the axis-Y-direction upper end of the effective light ray range of the second transmissive surface 43 and the upper peripheral light ray 52 a of the lower end light flux 52 passing through the axis-Y-direction lower end of the effective light ray range 50 intersect each other in the plane YZ, to the lower intersection 54, where the lower peripheral light ray 51 b of the upper end light flux 51 and the lower peripheral light ray 52 b of the lower end light flux 52 intersect each other in the plane YZ. The pupil P is formed between the reflector 34 and the second transmissive surface 43. The pupil P inclines with respect to the imaginary vertical line V perpendicular to the second optical axis M of the reflection surface 41 in the plane YZ.

Lens Data

Data on the lenses of the projection system 3E are listed below. The surfaces of the lenses are numbered sequentially from the reduction side toward the enlargement side. Reference characters are given to the lenses, the first deflector, the second deflector, the light-incident-side projection surface, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface. Data labeled with a surface number that does not correspond to any of the lenses, the first deflector, the second deflector, the light-incident-side projection surface, the reflection surface, the reflector, the first transmissive surface, and the second transmissive surface is dummy data. Reference character R denotes the radius of curvature. Reference character D denotes the axial inter-surface distance. Reference character C denotes the aperture radius. Reference characters R, D, and C are each expressed in millimeters.

Reference Surface Refraction/ character number Shape R D Glass material reflection C 18 0 Spherical Infinity 0.0000 Refraction 0.0000 1 Spherical Infinity 9.5000 Refraction 11.7000 19 2 Spherical Infinity 25.9100 SBSL7_OHARA Refraction 13.1449 3 Spherical Infinity 0.2000 Refraction 15.7239 L1 4 Spherical 35.4215 10.4750 443314.8653 Refraction 16.3636 5 Spherical −37.0296 0.2000 Refraction 16.2009 L2 6 Spherical 124.1837 6.3938 454154.8344 Refraction 14.5415 L3 7 Spherical −29.4013 1.2162 2.0006:28.214 Refraction 14.0000 8 Spherical 59.5041 0.2089 Refraction 14.3901 L4 9 Spherical 36.6649 11.7954 444852.8471 Refraction 15.1102 L5 10 Spherical −20.0854 1.2000 2.0010:29.134 Refraction 15.2728 11 Spherical −46.8668 0.2405 Refraction 17.0887 L6 12 Aspheric 88.2703 3.2943 735074.5321 Refraction 19.0117 13 Aspheric 50.5058 0.2128 Refraction 19.2901 L7 14 Spherical 46.6480 11.7146 456203.7378 Refraction 19.8069 15 Spherical −42.2516 21.9375 Refraction 20.2330 O 16 Spherical Infinity 0.0000 Reflection 31.3716 17 Spherical Infinity −22.2165 Refraction 21.5781 18 Spherical Infinity −0.2311 Refraction 22.6808 L8 19 Spherical −59.3719 −7.0715 2.0005:19.475 Refraction 22.9207 20 Spherical 735.6722 −1.3341 Refraction 22.5338 21 Spherical Infinity −20.5635 Refraction 21.8161 L9 22 Aspheric 37.4859 −1.2000 2.0027:19.317 Refraction 19.0086 23 Aspheric 4094.4011 −2.7557 Refraction 19.9946  L10 24 Spherical −75.4732 −10.6449 647255.4076 Refraction 23.0115 25 Spherical 56.1392 −23.6931 Refraction 23.2989 26 Spherical Infinity 0.0000 Reflection 32.5119 27 Spherical Infinity 23.6931 Refraction 21.7554  L11 28 Spherical 63.2789 12.7993 612767.3176 Refraction 20.3041  L12 29 Spherical −30.8281 6.1889 2.0020:19.359 Refraction 19.9647 30 Spherical 72.5265 13.1602 Refraction 20.7543  L13 31 Spherical −61.7004 4.4566 537239.4139 Refraction 23.3612  L14 32 Spherical −42.0251 6.5691 816278.2248 Refraction 24.0343 33 Spherical −31.8478 0.2000 Refraction 25.0031  L15 34 Aspheric −252.1895 10.0000 ‘Z-E48R’ Refraction 24.7280 35 Aspheric 28.5103 10.3567 Refraction 21.9118 36 Spherical Infinity 0.0000 Refraction 22.9461 37 Spherical Infinity 33.6948 Refraction 22.9461 44 38 Aspheric −49.4134 2.8111 ‘Z-E48R’ Refraction 32.4428 41 39 Aspheric −34.9985 −2.8111 ‘Z-E48R’ Reflection 34.7017 44 40 Aspheric −49.4134 −41.9647 Refraction 31.8814 34 41 Spherical Infinity 0.0000 Reflection 50.8876 42 Spherical Infinity 42.0161 Refraction 50.8876 43 Spherical Infinity 0.0000 Refraction 141.6424 42 44 Aspheric −46.9659 2.8111 ‘Z-E48R’ Refraction 51.5235 43 45 Aspheric −50.7702 0.0000 Refraction 75.0046 46 Spherical Infinity 307.4195 Refraction 217.6765 S 47 Spherical Infinity 0.0000 Refraction 1488.5481

The aspheric coefficients of each of the aspheric surfaces are listed below.

Surface number S12 S13 S22 S23 Radius of 88.27026489 50.50584329 37.48592767 4094.401136 curvature in axis-Y direction Conic constant 1.568 −1.3 −1 −0.88 (k) Fourth-order −1.10349E−05 −7.88464E−06 −6.81021E−07 −5.47787E−06 coefficient (A) Sixth-order 3.44274E−08 3.49784E−08 −1.59217E−09 5.07966E−10 coefficient (B) Eighth-order −2.07712E−11 −2.99526E−11 9.85211E−14 −3.75235E−13 coefficient (C) Tenth-order 4.62378E−15 1.40174E−14 coefficient (D) Twelfth-order coefficient (E) Fourteenth-order coefficient (F) Surface number S34 S35 S38 S39 Radius of −252.189464 28.51032743 −49.41336502 −34.99850714 curvature in axis-Y direction Conic constant 90 0 0.758064337 −1 (k) Fourth-order 1.16695E−05 −3.05019E−05 −1.00951E−05 1.20305E−06 coefficient (A) Sixth-order 7.16140E−08 1.86410E−07 1.15029E−08 −6.10403E−09 coefficient (B) Eighth-order −3.30028E−10 −5.07229E−10 −1.20410E−11 8.66480E−12 coefficient (C) Tenth-order 6.66535E−13 6.31522E−13 1.79838E−14 −5.09972E−15 coefficient (D) Twelfth-order −6.92904E−16 −4.55829E−16 −1.41251E−17 5.89237E−19 coefficient (E) Fourteenth-order 3.10765E−19 2.04805E−19 3.33978E−21 1.92772E−22 coefficient (F) Surface number S40 S44 S45 Radius of −49.41336502 −46.96586421 −50.77015164 curvature in axis-Y direction Conic constant 0.758064337 −0.865769094 −0.687556133 (k) Fourth-order −1.00951E−05 −6.36237E−06 2.54890E−06 coefficient (A) Sixth-order 1.15029E−08 4.35750E−09 −3.89464E−10 coefficient (B) Eighth-order −1.20410E−11 −9.84603E−13 2.49570E−14 coefficient (C) Tenth-order 1.79838E−14 coefficient (D) Twelfth-order −1.41251E−17 coefficient (E) Fourteenth-order 3.33978E−21 coefficient (F)

The maximum object height, the numerical aperture, the mirror radius, the lens overall length, and TR of the projection system 3E are as follows: The maximum object height is the dimension from the first optical axis N of the projection system 3E to the farthest point therefrom in the image formation region of the surface of each of the liquid crystal panels 18. The maximum object height is expressed in millimeters. The numerical aperture is abbreviated to NA. The mirror radius is the radius of the first reflection surface in millimeters. The final lens radius is the lens radius of the second transmissive surface in millimeters. The lens overall length of the projection system 3E is the distance in millimeters from the liquid crystal panels 18 to the second transmissive surface in the axis-Z direction. TR stands for the throw ratio and is the quotient of the operation of dividing the projection distance by the axis-X-direction dimension of a projection image projected on the screen S.

Maximum object height 11.7 NA 0.3125 Mirror radius 34.7 Final lens radius 75.1 Lens overall length 318 TR (0.59″WXGA) 0.188

Effects and Advantages

The projection system according to the present example can provide the same effects and advantages as those provided by the projection system according to Example 4.

In the present example, the lens L15 of the first optical system 31 and the reflector 34 overlap with each other when viewed in the direction perpendicular to the optical axis of the first optical system 31. The first optical system and the second optical system therefore approach each other in the direction of the optical axis of the first optical system, whereby the size of the projection system can be reduced in the optical axis direction.

FIG. 21 shows the enlargement-side MTF of the projection system 3E. The projection system 3E according to the present example provides high resolution, as shown in FIG. 21. 

What is claimed is:
 1. A projection system comprising: a first optical system; and a second optical system including an optical element and a reflector and disposed at an enlargement side of the first optical system, wherein the optical element has a reflection surface, a first transmissive surface disposed at the enlargement side of the reflection surface, and a second transmissive surface disposed at the enlargement side of the first transmissive surface, the reflector is disposed at the enlargement side of the reflection surface and at a reduction side of the first transmissive surface, and the reflector is disposed between the optical element and the first optical system in a direction along a first optical axis of the first optical system.
 2. A projection system comprising: a first optical system; and a second optical system including an optical element and a reflector and disposed at the enlargement side of the first optical system, wherein the optical element has a light-incident-side transmissive surface, a reflection surface disposed at the enlargement side of the light-incident-side transmissive surface, a first transmissive surface disposed at the enlargement side of the reflection surface, and a second transmissive surface disposed at the enlargement side of the first transmissive surface, the reflector is disposed at the enlargement side of the reflection surface and at a reduction side of the first transmissive surface, light passing through the light-incident-side transmissive surface and reflected by the reflection surface is incident on the light-incident-side transmissive surface again and travels toward the reflector, and the reflector is disposed between the optical element and the first optical system in a direction along a first optical axis of the first optical system.
 3. The projection system according to claim 2, wherein the light-incident-side transmissive surface is an aspheric surface.
 4. The projection system according to claim 1, wherein the reflection surface has a concave shape.
 5. The projection system according to claim 1, wherein the second transmissive surface has a convex shape protruding toward the enlargement side.
 6. The projection system according to claim 1, wherein the first transmissive surface has a convex shape protruding toward the enlargement side.
 7. The projection system according to claim 1, wherein the reflection surface is an aspheric surface.
 8. The projection system according to claim 1, wherein the second transmissive surface is an aspheric surface.
 9. The projection system according to claim 1, wherein the first transmissive surface is an aspheric surface.
 10. The projection system according to claim 1, wherein the reflector includes a flat mirror.
 11. The projection system according to claim 1, wherein the reflection surface is located at one side of a second optical axis of the reflection surface, and the reflector, the first transmissive surfaces, and the second transmissive surface are located at other side of the second optical axis.
 12. The projection system according to claim 2, wherein the reflection surface and the light-incident-side transmissive surface are located at one side of a second optical axis of the reflection surface, and the reflector, the first transmissive surfaces, and the second transmissive surface are located at other side of the second optical axis.
 13. The projection system according to claim 11, wherein axes X, Y, and Z are three axes perpendicular to one another, an axis-X direction being a width direction of an enlargement-side image formation plane, an axis-Y direction being an upward/downward direction of the enlargement-side image formation plane, and an axis-Z direction being a direction perpendicular to the enlargement-side image formation plane, a pupil that connects an upper intersection to a lower intersection inclines with respect to an imaginary vertical line perpendicular to the second optical axis in a plane YZ containing the first and second optical axes, the upper intersection is an intersection where an upper peripheral light ray of an upper end light flux passing through an upper end of an effective light ray range of the second transmissive surface that is an upper end in the axis-Y direction and an upper peripheral light ray of a lower end light flux passing through a lower end of the effective light ray range that is a lower end in the axis-Y direction intersect each other in the plane YZ, and the lower intersection is an intersection where a lower peripheral light ray of the upper end light flux and a lower peripheral light ray of the lower end light flux intersect each other in the plane YZ.
 14. The projection system according to claim 1, wherein the first optical system includes a first deflector that deflects an optical path of the first optical system.
 15. The projection system according to claim 14, wherein an angle between a first section of the first optical axis that is a section at the reduction side of the first deflector and a second section of the first optical axis that is a section at the enlargement side of the first deflector is 90°.
 16. The projection system according to claim 14, wherein the first optical system includes a second deflector that deflects the optical path toward the enlargement side of the first deflector.
 17. The projection system according to claim 16, wherein an angle between the second section of the first optical axis, which is a section at the reduction side of the second deflector, and a third section of the first optical axis that is a section at the enlargement side of the second deflector is 90°.
 18. The projection system according to claim 17, wherein the first section and the third section are parallel to each other.
 19. The projection system according to claim 1, wherein an intermediate image is formed between the first optical system and the reflection surface.
 20. A projector comprising: the projection system according to claim 1; and an image formation section that forms a projection image in a reduction-side image formation plane of the projection system. 